IN-HOME OBESITY PREVENTION TO REACH LOW-INCOME INFANTS THROUGH MATERNAL AND SOCIAL TRANSMISSION ABSTRACT The proposed comparative effectiveness research capitalizes on the strengths and capabilities of Home Visitation Programs (HVPs), to deliver in-home obesity prevention to low-income infants and their families from diverse racial and ethnic backgrounds, and correct disparities in priority populations. Annually, over 500 publicly and privately funded HVPs provide services to 650,000 low-income, at-risk infants and their families in the United States, yet HVPs have not yet systematically targeted childhood obesity. Over the last four years, we have integrated evidence-based obesity prevention components into the services provided by our partner HVP, a collaborative initiative called COPE: Childhood Obesity Prevention @ homE /Contrarrestar Obesidad: Programa para nios En casa. Our pilot work successfully integrated COPE into the ongoing, weekly, in-home visits of our HVP partner for six months, alongside their standard curriculum. The proposed research builds upon our pilot work and partnerships to test the larger-scale effectiveness of delivering primary (infants) and secondary (mothers) obesity prevention as part of HVP services for the full 2-year duration of these services. Specifically, 400 low income mothers and their infants (70% Hispanic/Latino, 13% African American, 8% White, 5% American Indian/Alaskan, 4% mixed/other race) already receiving HVP services will be enrolled into the study, for an effective final sample of 300 mothers/infants. Home visitors delivering services will be randomly assigned to deliver the standard HVP curriculum only or HVP + COPE. Mothers and infants will be assessed at enrollment and after receiving the intervention for 12 and 24 months. Aim 1. Test the direct effects of COPE on infants and mothers? weight, metabolic risks, diet/energy intake, and physical activity. This will be accomplished by comparing changes in body weight, metabolic markers, and eating and activity-related behaviors between infants/mothers across study arms (HVP only vs. HVP+COPE). These results will indicate whether the HVP is an effective infrastructure for primary and secondary obesity prevention. Aim 2. Test whether breastfeeding and maternal diet and activity, feeding practices, and food insecurity mediate the effect of COPE on infants? outcomes. This aim will test mechanisms of maternal transmission on infants? obesity risks. Aim 3 is two-pronged. Aim 3a tests the direct effect of HVP+COPE (vs. HVP only) on the characteristics of the social and community networks that surround mothers and infants (i.e., the density, composition, and quality of their ?health support networks?). Aim 3b tests whether the characteristics of social networks mediate the effects of COPE on maternal and infant outcomes. These findings will indicate if HVP obesity prevention efforts can alter and/or activate social network mechanisms. A Secondary Aim of this project is to conduct a real-life economic analysis (costs, cost- savings and non-monetary benefits) of integrating COPE into existing HVPs. The project is poised to test an innovative, scalable, sustainable, and potentially cost-effective model for preventing obesity among children who are at the greatest risk for health inequities.